1. Technical Field
Aspects and features of the present invention relate to a collimator magnet (“CM”) for use in an ion implantation system to compensate for beam deflection. More specifically, the present invention relates to a collimator magnet achieving substantially high parallelism for an ion beam, as well as compensation of the fringe field, and optionally space charge effects.
2. Related Art
In the related art, an ion implantation system may be used to implant ion species onto a wafer. For example but not by way of limitation, ion species may be implanted on a silicon wafer to manufacture a semiconductor device.
FIG. 1 illustrates a related art implementation of an ion implantation system. A related art ion implantation system is disclosed in U.S. Pat. No. 6,614,027B1, which is also assigned to the same assignee as the present application, and is incorporated herein by reference. More specifically, the related art ion implantation system is of a type known as EXCEED.
As shown in FIG. 1, an ion source 2 is provided that generates an ion beam 4, which travels along a beam line through mass analysis magnet 6, accelerating tube 8, trimming Q lens 10 and energy analysis magnet 12. Eventually, the ion beam 4 reaches a beam sweeping magnet (BSM) 14, where the beam becomes divergent. A collimator magnet 16 functions to make parallel a divergent beam from ion source 2. The beam that has passed through the collimator magnet 16 is then used in the end station 18, 20, 22, for example, to implant an ion species on a semiconductor wafer.
U.S. Pat. No. 5,834,786 discloses another related art ion implantation system, as shown in FIG. 2. More specifically, collimator magnet 3′ is provided. The collimator magnet 3′ receives divergent rays of an incoming beam and outputs apparently parallel rays. The ion beam received from the ion generation source may be a spot beam; alternatively, the ion beam may be a ribbon beam.
However, the above related art ion implantation systems may have various problems and/or disadvantages. For example, but not by way of limitation, magnetic leakage occurs in a fringe field of a related art collimator magnet, and the related art collimator magnets are not capable of compensating for this effect with a substantially high degree of precision. Related art collimator magnets cannot precisely make the divergent beam parallel, due to magnetic leakage (hereinafter referred to as a “fringe field effect”). If the beam is not made parallel, then the ion implantation of the beam perpendicular to the wafer cannot be fully performed. Further, the related art cannot compensate for the space charge effect problem, discussed further below.
The degree of precision with which related art collimator magnets can take into account the above-discussed related art fringe field effect problem is limited. For example, available related art knowledge, available related art computational power (both hardware and software), and related art industry standards imposed for precision of beam parallelism have limited the degree of precision that is possible for taking into account magnetic field fringe effects. Such related art collimator magnets may be used to make semiconductor wafers when a minimum circuit pattern width of semiconductor device was around 250 nm as manufacture standard at that time (i.e., year 2001).
However, the minimum circuit pattern width of a semiconductor device has since been substantially changed. The minimum circuit pattern width will become about 25 nm to 45 nm as a manufacture standard, from the above-noted value of about 250 nm. Moreover, the size of the wafers which currently have 300 mm is diameter increasing as well, for example to 450 mm. Accordingly, the result of the fringe field effect as well as space charge effects need to be properly compensated for to achieve parallelism of the ion beam in a manner that permits the ion implantation system to effectively operate. In this regard, there is an unmet need to obtain a solution that addresses one or both of these effects.